1. Field of the Invention
The present invention relates to a light guide plate, an illumination device and a method for adjusting a light guide plate; and more particularly, the present invention relates to a light guide plate with an adjustable illumination angle, an illumination device with an adjustable illumination angle, and a method for adjusting the illumination angle of a light guide plate.
2. Descriptions of the Related Art
Conventional light guide plates usually are edge-type light guide plates in combination with light emitting diodes (LEDs). An illumination angle of such a light guide plate is unchangeable and is controlled by the microstructures on the light guide plate. In other words, a desired illumination angle must be determined in advance before the microstructures are formed, and the illumination angle is unchangeable. Therefore, different light guide plates must be used when different illumination angles are desired.
FIG. 1 illustrates a schematic view of an illumination device 100 disclosed in Taiwan Patent Application No. 098136506. The illumination device 100 comprises a light guide plate 110, a plurality of microstructures 118 disposed on the surface of the light guide plate 110, a light source 120 and a prism sheet 130. A light beam emitted from the light source 120 enters into the light guide plate 110. Then, by means of the microstructures 118 which disrupt the total reflection, a part of the light beam is reflected to leave the light guide plate 110 from the first surface 112 of the light guide plate 110; and the remaining part of the light beam leaves the light guide plate 110 from the second surface 114 of the light guide plate 110 and is reflected by a reflective plate 160 to enter into the light guide plate 110 again, and then leaves the light guide plate 110 from the first surface 112. Finally, an illumination angle of light left from the first surface 112 is adjusted by the prism sheet 130. For conventional illumination devices, the prism sheet and the microstructures must be custom designed according to specific requirements, which makes it difficult to adjust the illumination angle depending on the practical scenarios and requirements of practical use.
Accordingly, it is important to provide an illumination device that allows for the flexible adjustment of an illumination angle thereof in practical operations.